1. Field of the Invention
The present invention relates to a sewing machine including a laser cutting system capable of successively and accurately cutting a sheet of cloth, leather, or the like. Furthermore, the present invention relates to a sewing method and an embroidering method preferably to be carried out using such a sewing machine. More particularly, the present invention relates to a sewing machine including a laser cutting system, to be used for smoothly and accurately sewing a plurality of sheets together, or for making embroidery in an openwork pattern or a stitch pattern along a periphery of the sheet or along a periphery of an opening formed in the sheet. In addition, the present invention relates to a sewing method and an embroidering method preferably to be carried out using such a sewing machine.
2. Description of the Prior Art
For making embroidery in an openwork pattern or the like along a periphery of a base sheet of cloth, leather or the like, or along a periphery of an opening formed in the base sheet, a back sheet is required to entwine with embroidery threads at portions where the base sheet is absent. The back sheet should be made of a material strong enough to withstand even being entwined with the embroidery threads. According to a conventional embroidering method, such a back sheet is laid under the base sheet after the base sheet is cut in a prescribed shape with scissors, a cutter, a blade, a water jet, plasma, or the like. The back sheet is arranged so as to be projected beyond the periphery of the base sheet or to be projected inside of or extending across an opening formed in the base sheet. Thus, embroidery is made across or along the periphery of the base sheet (or the periphery of the opening) and the projecting portion of the back sheet.
According to another conventional embroidering method, after the base sheet is arranged on the back sheet, only the base sheet is cut in a prescribed shape with scissors, a cutter, or the like. Thereafter, embroidery is made across or along the periphery of the cut base sheet and the back sheet projecting beyond the periphery (or across or long the periphery of the formed opening and the back sheet remaining inside of the opening). Then, the back sheet is finally removed leaving the embroidery along the periphery of the base sheet 5 (or along the periphery of the opening).
On the other hand, according to a conventional sewing method employed for manufacturing clothes, shoes, bags, etc., a base sheet of cloth, leather, or the like is cut in a complicated shape with scissors or the like and then the periphery of the cut base sheet is sewed together with another base sheet.
It has recently became practice to industrially carry out the above-described methods using industrial sewing machines. For example, in order to manufacture embroidery goods using a sewing machine, a base sheet, which is previously cut in a prescribed shape, is laid on a back sheet. Then, under such a condition, both of the base sheet and the back sheet are held in a sheet holding frame provided on a sewing machine table. Then, the sheet holding frame is moved directions in an X-Y plane (horizontal directions) in synchronization with vertical movement of a needle bar in the same manner as that of an ordinary embroidering method. As a result, embroidery can be made along the periphery of the base sheet or along the periphery of an opening formed in the base sheet.
As is described above, it is necessary to cut the base sheet in a prescribed shape prior to making embroidery. However, a conventional sewing machine itself fails to have a cutting system, so that the base sheet must be cut previously with scissors, a cutter, or the like, which causes a deterioration efficiency of operation. In addition, the thus cut base sheet must be accurately set in the sheet holding frame on the sewing machine table so that the periphery of the base sheet will correspond to a needle bar of a sewing machine head, which cause further deterioration of operation efficiency. Furthermore, it is not easy to manually cut the base sheet in a complicated shape. If a cutting device is employed for cutting the base sheet in a complicated shape, the manufacturing cost will be raised.
To overcome the above described problems, Japanese Patent KOKOKU No. 6-33550 discloses a sewing machine including a laser cutting system capable of cutting a sheet with laser light emitted from a cutting device controlled by a control section included in the sewing machine. According to such sewing machine, the cutting device is controlled on the basis of control signals for making stitches on the sheet. Therefore, the sheet is intermittently and two-dimensionally moved by a sheet feeder, while it is cut with laser light which is intermittently oscillated so as to synchronize with the intermittent movement of the sheet.
With such structure in which laser light is oscillated synchronization with the sheet feeder, the output level of the laser light is inevitably unstable due to the short time of the laser light oscillation. As a result, there is a possibility that the sheet may will be burned partially and/or that the sheet will not be cut successively and accurately. There arises another problem in that the periphery of the cut sheet becomes poor in appearance due to the unstable cutting operation.
Furthermore, as is described above, for making embroidery in an openwork pattern along the periphery of the base sheet (or along the periphery of the opening formed in the base sheet), it is necessary to arrange an back sheet under the base sheet so as to project beyond the periphery of the base sheet (or to project inside of or across the opening). In such case, only the base sheet should be cut prior to the embroidering process. However, according to the structure where the laser light is intermittently oscillated and therefore the output level of the laser light is the inevitably unstable, there is possibility that the base sheet will not be cut completely and/or that the back sheet will be cut partially or completely together with the base sheet.